The present disclosure relates generally to a system for, and a method of, reading and tracking of radio frequency (RF) identification (RFID) tags associated with items located in a venue, and, more particularly, to enhancing the RFID reading performance, especially of high-priority tags that are moved in the venue.
Radio frequency (RF) identification (RFID) technology is becoming increasingly important for logistics concerns, material handling and inventory management in retail stores, warehouses, distribution centers, buildings, and like venues. An RFID system typically includes an RFID reader, also known as an RFID interrogator, and preferably a plurality of such readers deployed about the venue. Each RFID reader interrogates multiple RFID tags in its coverage range. Each RFID tag is usually attached to, or associated with, an individual item, or to a package for the item, or to a pallet or container for multiple items. Each RFID tag typically includes an antenna, a power management section, a radio section, and frequently a logic section containing a control microprocessor, a memory, or both. Each RFID reader transmits an RF interrogating signal, and each RFID tag, which senses the interrogating RF signal, responds by transmitting a return RFID receive signal. The RFID tag either generates the return RFID receive signal originally, or reflects back a portion of the interrogating RF signal in a process known as backscatter.
It is known to encode the RFID tag with an Electronic Product Code (EPC) identifier, which provides a unique identity for every physical item. The format and structure of the EPC identifier are defined in the EPCglobal Tag Data Standard, which is an open standard freely available from EPCglobal, Inc. The aforementioned return RFID receive signal is decoded into data by each reader, which thereby identifies, counts, or otherwise interacts with the associated item. The decoded data, also known as a payload, can denote a serial number, a manufacturer, a price, a date, a destination, another attribute(s), or any combination of attributes, and so on.
The RFID system is often used in an inventory monitoring application. For example, in order to take inventory of RFID-tagged items in a retail store, it is known to position one or more RFID readers overhead in the store, and then, to allow each reader to automatically read whatever tagged items are in the coverage range of each reader. The RFID system can also be used for locationing applications, i.e., for estimating and determining the location or bearing, i.e., the angular direction both in azimuth and elevation, of any particular tag relative to a particular reader or readers.
Yet, as advantageous as the known RFID system has been in accurately locating, monitoring, and tracking inventory items, experience has shown that there are times when real-world conditions may sometimes degrade the reading performance of the system. Typically, the tag environment is quite dense, because there is a multitude of tags in the venue, and at least some of the tags are in the process of being moved, or have already been moved once or several times, through the venue. Often, not all the tags are of interest, and sometimes, it is desirable to interrogate only tags that are deemed to be of interest. However, the known RFID system typically interrogates all the tags, thereby wasting time and processing on reading the tags of no interest. In addition, individual tag tracking can be challenging due to the time that it takes to quiet tags of no interest. Moreover, the venue may contain shelving, fixtures, equipment, vehicles, and the like, not to mention the floor, the ceiling and the room walls, each or all of which can reflect and scatter the interrogating RF signal and/or the return RFID receive signal, thereby compromising the reading performance due to multi-path reflections, destructive interference among signals and with stray signals, ambient temperature variations, etc.
Accordingly, there is a need to locate, monitor, and track RFID tags, especially only those of interest, in a venue, especially in a real-world environment.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.